Cobber's Cobra

[BlackUZZ31]

 

[milisakeracing]

Exceptional paint job! Would love to put together one of these or a Caterham 7 with the UZ power plant. Someday

 

[1uzvl]

are you still running the water/meth injection??

Has anything been done to the engine to run 11psi at 8000rpm??

 

[Cobber]

Yep still running the water meth injection. 50:50 by weight roughly 40:60 by volume. I control the water meth with the Adaptronic. PWM output to control the pump is on at 20% > 110kpa going up to 100% > 160 kpa. Logic input must be > 1,200 rpm to activate pump to stop low rpm drowning. Logic input for low water meth tank changes fuel and timing table and locks out water meth pump from operating and running dry.

Engine is un opened, soft rev limit is 7,500 hard rev limit is 8,000. I have hit the soft limit but not the hard. I have changed gear way before hitting the soft limit 99% of the time. The torque is down lower with this blower so it is a waste of time revving the nuts off the engine. I m going to change the soft to 7,000 and hard to 7,300.

Still having a lot of fun playing with this car and went for a great run on the weekend.

 

[JustenGT8]

You can lower it further again i suspect Cobber. Try one of the online shift calculators. With you short runner manifold you'll get a few 100rpm more than me but my shifts are optimal down around 6500rpm and lower. I only hold it to a higher rpm in top and at the track where holding a few more rpm is quicker than an extra shift.

 

[Cobber]

Thanks Justen, Yes I also find around 6 - 6,500 rpm optimum. I have a spreadsheet that works out peak torque for each gear and optimum gear change rpm each but at the end of the day it's you ears and your bum that tell you when to shift.

Being able to hold on to 2nd or 3rd gear a bit longer makes the higher rpm cut a bit more useful on some tracks, it is a balance between engine safety and advantage over people who are up and down gears.

 

[1uzvl]

Where are you running the meth through? before or after the blower.

 

[Cobber]

7 gph nozzle pre blower just behind the throttle body.

http://www.alcoholinjectionsystems.com/Water-Injection-Nozzle/c28/index.html?page=2

This brings the post supercharger temps pretty much back to ambient temp.

 

[Cobber]

This is the pump I am running, factory set at 200 psi still.

http://www.alcoholinjectionsystems....ter-Methanol-Injection-Pump/product_info.html

 

[1uzvl]

Oh ok, the reson i ask is harrop dont recommend running anything through their blowers something about taking of the teflon coating or so im told. You views??

Im umm'n and argh'n bout getting a kit so just doing some research on it.

 

[1uzvl]

because i cant edit: i mean blower/bullet kit.

 

[Cobber]

Yes I have been told the same by Harrop when I bought it. Interesting how Bullet who sell the Harrop supercharger actually put an extra fuel injector in their inlet manifolds!?.

Like most things I decided to do what I think would work best and injected pre supercharger. Harrop use the Eaton rotors in their own housing as do Magnuson etc etc.

I have removed the charger twice now just to inspect the rotors and they are still as new without a mark. It's not a daily driver and not constantly on boost so for me it's not an issue. The rotors actually have a rough finish to them and to me it doesn't feel like tefon, I have no idea what it is.

Horses for courses you pays the money you makes the choice. I can only let you know my experience to date.


http://www.alcoholinjectionsystems.com/EatonSupercharger.html

 

[Sciflyer]

Hi matty, andy

I also have the Bullet HTV1900 kit and AIS water/meth kit and like Andy i am running a nozzle between the throttle and blower. Bullet will make you aware of the warranty issues regarding any liquid injection through the blower, however i got the feeling they were really doing that on Harrops' behalf rather than because they themselves had issues with it, so make of that what you will

I will say both Bullet and AIS were good to deal with, happy to run through options and advice

 

[Tuf Lux]

Bit late on the reply here but this info may be of some help to others.

I spoke to one of the engineers at Harrop a while back about my blower, as I am running the extra injector at the supercharger inlet and have changed over to E85 fuel. With all the talk around about the corrosive nature of the ethanol based fuels, I thought it was best to check with them. They told me they have had problems in the past with methanol injection taking the coating of the rotors but said I should be fine with what I was wanting to do.

 

[Cobber]

I pulled my supercharger off before Christmas to move the post air temp sensor to directly under the rotors instead of at the back of the manifold. Two years of spraying water meth in to the front of my supercharger and the rotors are still like new. As stated before my car is not a daily driver but it does get a run at least every other weekend and I do carry out boost checks........

The helmholtz effect will cause air and fuel mixture to be present in the lower manifold. This mixture recirculates through the supercharger when not under boost. The rotors move more air than the engine needs so the excess air and fuel mixture when not under boost goes back through the butterfly and in to the intake of the supercharger. Most of this fuel will be in gas form but not all. This means a certain am out of wet fuel (all be it small) is always going through the rotors.

I wish I had taken some pictures. The inlet valves were also all spotlessly clean.

 

[Tuf Lux]

The gentleman I spoke to didn't actually specify if it was a HTV which they had experienced problems with. He was more just talking about the superchargers and coatings in general, saying that they have had problems with that injection method at some point.

As the common consensus seems to be that it's the older style blowers and coatings if any, are the ones that have the problems. With how far technology has come in so many areas, you wouldn't expect something simple like this to be a problem anymore. And at the end of the day, if it's working fine for you and even keeping things cleaner, then its smiles all round.

On a side note Andy, those valve covers of yours, is that a polished finish on them or some form of ceramic coating, etc?

 

[Cobber]

Cam covers were polished by hand.

Cobra has now been sold but happy to answer any questions on the build.

 

[JustenGT8]

Sold? Damn, and no ad on here to give us a chance to dream anyways

 

[Cobber]

Hi Justen, I sold it 6 months ago I was just making sure I removed pictures from forums as I no longer own the vehicle. It was listed on carsales.com. I'm thinking about an Ultima for the next project.

Thanks for everyone's help and suport on this forum.

 

[BlackUZZ31]

what was the final numbers / dyno sheet for this thing?